The present invention relates to a melt spinning apparatus for synthetic yarns and, more particularly, to a melt spinning apparatus capable for spinning yarn having an excellent quality of the unevenness of fineness being reduced.
A general melt spinning apparatus of the prior art for manufacturing synthetic resin yarns of polyester or polyamide is constructed, as shown in FIG. 5. Namely, there is arranged a cooling device 51 below a spinning unit 50, and there is arranged a take-up device 52 below the cooling device 51. In the spinning unit 50, there is mounted a spinning pack 54, in which a spinning plate 53 is mounted. The molten polymer is spun as a plurality of filaments f from a plurality of nozzles 55 which are formed in the spinning plate 53. The plurality of filaments f are individually cooled and set with the cooling wind blown from a filter 56 of a cooling device 51 and are taken up on the take-up device 52 after oiled by an oiler roller 57.
In the melt spinning apparatus of the prior art, however, the cooling wind to be blown from the filter 56 of the cooling device 51 flows in only one direction generally perpendicular to the running direction of a spun yarn Y. Depending upon the positions of the plurality of nozzles 55 formed in the spinning plate 53, therefore, the individual filaments f have different states in which they are cooled with the cooling wind, so that they are liable to have different qualities. When the individual filaments f are finally collected as the yarn Y, therefore, there arises a problem that the yarn Y has a large unevenness of fineness (U %) and cannot have a satisfactory quality.
Moreover, the cooling wind blows in only one direction. Depending upon the flow rate of the cooling wind, therefore, the plurality of filaments f are so fluctuated in curved states that they may contact with each other to fuse together. This fusing phenomenon may cause a problem that the unevenness of fineness is enlarged and also a filament breakage is caused. Especially in the case of a large flow rate of the cooling wind, an ascending current occurs in the vicinity of the spinning plate 53 to make the surface temperature of the spinning plate 53 lower and thereby the spinning of the molten polymer unstable. This phenomenon of lowering the surface temperature of the spinning plate 53 is also a cause for increasing the unevenness of fineness or breaking filament.
An object of the present invention is to provide a melt spinning apparatus capable to reduce the unevenness of finenesss of melt spun yarn.
Another object of the present invention is to provide a melt spinning apparatus capable to prevent the breakage of the melt spun yarn.
In order to achieve the above-specified objects, the present invention provides a melt spinning apparatus comprising: a spinning unit disposing a spinning plate having a plurality of nozzles and a cooling device disposed below the spinning plate, wherein the nozzles of the spinning plate are arranged annular in at least one circle, and a cylindrical filter is disposed at an exit of a cooling wind in the cooling device so as to enclose around a spun yarn discharged from the spinning plate.
In the above construction, an annular diameter of the nozzles arranged annular is from no less than 0.6 times to no more than one time of the internal diameter of the cylindrical filter, and the flow velocity of the cooling wind blown from the cylindrical filter is distributed gradually higher according to the downstream of the spun yarn.
As described above, the plurality of nozzles in the spinning plate are so arrayed in at least one circle that they may have an annular diameter of no less than 0.6 times of the internal diameter of the cylindrical filter. On the other hand, in the cooling device, the cylindrical filter is arranged to enclose around a group of filaments spun from a group of the nozzles in an annular array.
Accordingly, the cooling wind blows uniformly around the group of the filaments, so that each of the filaments can be uniformly cooled down. Moreover, the velocity of the cooling wind is so set that it is lower on the upstream side where the coagulation of the spun filaments is not yet complete, but higher on the downstream side where the coagulation has proceeded, thereby to make the filaments coagulated with less uneveness of fineness. Moreover, the flow velocity of the cooling wind is made the slower on the more upstream side so that the surface temperature of the spinning plate can be suppressed to be dropped even if the total flow is increased.
In the aforementioned melt spinning apparatus, for the plurality of grouped nozzles disposed at the spinning plate, it is desired that the center distance between the adjoining nozzles is no less than 8 times of the nozzle diameter. It is, therefore, possible to prevent the filaments from fusing to each other.
For the cooling device, it is desired to provide a cylindrical fow guide of a cooling wind so as to enclose the outer circumference of the cylindrical filter, an inner wall of which is inclined closer to the cylindrical filter on the upper side. By this arrangement of the cylindrical flow guide, there is easily made the distribution in which the flow velocity of the cooling wind is slower on the upstream side of the spun yarn and faster on the downstrean side.
Moreover, a plurality of rectifying vanes may be arranged on the inner wall of the cylindrical fow guide to extend radially toward the center of the cylindrical filter and at intervals in the circumferential direction. Moreover, it is desired to connect a guide tube to the lower end of the cylindrical filter.